Our studies have continued on the isolation and characterization of the nuclear protein matrix. This nuclear component forms the structural framework of the mammalian nucleus and determines the shape of the nucleus. The matrix has been characterized as containing 3 acidic proteins of a molecular weight of 67,000 to 69,000. These proteins represent residual components of the nuclear membrane, interchromatinic space and residual nucleolus. We are presently determining the ability of this matrix to be phosphorylated prior to the onset of DNA synthesis. We are also studying other chemical variations of the matrix related to the hormone sensitive and insensitive prostatic tumors. We have reported that the nuclear matrix is associated with the component of DNA that is rapidly labeled during the DNA synthesis and appears to be the site of DNA replication. We have isolated this structure from several mammalian tissues including the prostate. Our studies with antiandrogens have elucidated several pathways by which these new drugs inhibit prostatic growth. We have reported on the ability of some of these drugs to inhibit the testosterone synthesis in the testes by blocking the isomerase enzymes. Other studies have also indicated the ability of the antiandrogens to interfere with steroid glucuronide synthesis in prostatic tissue. BIBLIOGRAPHIC REFERENCES: Allen, S.L., R. Berezney, and D.S. Coffey. Phosphorylation of Nuclear Matrix Proteins in Isolated Regenerating Rat Liver Nuclei. Biochemical and Biophysical Research Communications, 75, 111-116, 1977. Barrack, E.R. and D.S. Coffey. Amino Acid Incorporation into the Nuclear Matrix of Rat Liver Nuclei. Fed. Proc., 36, 990, 1977.